1. Field of the Invention
This invention relates, generally, to retort processes for extracting hydrocarbon fuels from low-value feedstocks, such as oil shale and carbonaceous municipal solid wastes. More particularly, the invention relates to concurrent, thermally-coupled retort extraction processes for disparate feedstocks.
2. Description of Related Art
Various alternative energy production processes, using partial combustion, combustion and/or heat retorting, have been proposed and implemented for releasing, capturing and refining hydrocarbons from low-value carbonaceous feedstocks, such as tar sands, oil sands, oil shale and pulverized municipal sold waste (“MSW”). The recovered hydrocarbons, which are typically in the form of liquids and/or low-carbon-number alkanes, generally require further processing and reforming in order to optimize their utility. As a rule, the processes used to extract hydrocarbon compounds from each of the disparate carbonaceous feedstocks are anaerobic, and utilize unique ranges of temperature and pressure.
For example, to enhance recovery and thwart excess decomposition of hydrocarbons due to over-heating, Dana (U.S. Pat. No. 7,862,705) discloses a method of recovering hydrocarbons from hydrocarbonaceous materials that can include forming a constructed permeability control infrastructure. This constructed infrastructure defines a substantially encapsulated volume. Comminuted hydrocarbonaceous material can be introduced into the control infrastructure to form a permeable body of hydrocarbonaceous material. The permeable body can be heated sufficient to remove hydrocarbons therefrom. During heating, the hydrocarbonaceous material is substantially stationary as the constructed infrastructure is a fixed structure. Specifically, when proto-petroleum-like kerogen laden oil shale is slowly retorted in the encapsulated infrastructure at a lower temperature, higher quality lighter gravity API oil ready for upgrading using hydro-treating is recovered having no fines or bottoms.
Klepper (U.S. Pat. No. 7,655,215) has also shown that lower temperatures and slower process times can be used to capture and process a variety of hydro-carbonaceous material into useful byproducts. Conversely, at very high processing temperatures, incineration and full combustion gasification of the kerogen-based feedstocks takes place. Klepper alternatively discloses an apparatus operating at differing temperatures in different oxygen-free zones designed to form syngas from carbonaceous materials such as coal that includes a devolatilization reactor in combination with a reformer reactor which subsequently forms syngas (a gas mixture that containing varying amounts of carbon monoxide and hydrogen). The reformer reactor, in turn, is in communication with a particulate separator. The devolatilization reactor is fed with material using a compression feeder which drives air from the feed material, compresses it in a feed zone forming a seal between the feed hopper and the devolatilization reactor. The reformer reactor, as well as the particulate separators, is maintained in a heated furnace so that the temperature of the formed syngas does not decrease below the reaction temperature until particulate material has been separated. Klepper pioneered the use of separation of working zones for retorting mixed feedstocks and conveying said heated materials within the system using the disclosed methods.
Clayson (“Combustion of Municipal Solid Wastes with oil Shale in a Circulating Fluidized Bed,” Department of Energy Grant No. DE FG01 94CE15612, Jun. 6, 1996, Energy Related Inventions Program Recommendation No. 612, Inventor R. F. Clayson, NIST.) first describes combustion of oilshale with municipal solid waste (“MSW”). Clayson, et. al., disclosed integrated process for the treatment of MSW combined with oil shale. In this process, after recycling steps to save usable materials such as aluminum, other metals, and glass have been completed, the resulting refuse-derived fuel (“RDF”) reduced from the MSW was co-combusted with oil shale in a circulating fluidized bed. During combustion, the oil shale not only reportedly removed sulfur dioxides, chlorine compounds, and other pollution effluents, but it also added significant hydrocarbon fuel content and constituents to the overall gasified yield and the waste rock char byproduct also became a useful cementitious ash. Clayson, et. al. claims the possibility of creating an environmentally beneficial and financially viable integrated process in which the RDF helps produce electrical energy, the volume of solid waste is greatly reduced in both volume and weight, and RDF's potentially hazardous components can be encapsulated in a non-hazardous cementitious material that could serve other useful purposes. Accordingly, the authors of the publically funded DOE report assert the integrated process would eliminate the main environmental problems associated with MSW and its associated waste streams.
Enefit (Eesti Energia in Estonia) is the largest oil shale mining and processing company in the world. During more than 50 years of continuous surface retort production, Enefit has produced more than 200 million barrels of oil from oil shale. Enefit's technology employs a dryer, a rotary kiln reactor, and a furnace unit that is used to retort spent oil shale. The resulting hot ash is separated from the combustion gas and mixed with comminuted oil shale feedstock in the rotary kiln reactor. Combustion gases from the furnace unit are used to dry the comminuted oil shale feedstock in the dryer before mixing it with hot ash.
Other related prior art describes various methods relating to the properties of oil shale being heated to various temperatures and injected in various combustion processes. Boardman, et. al. (U.S. Pat. No. 7,384,615 and U.S. Pat. No. 7,708,964) virtually mirrors the findings in the Department of Energy funded Clayson Publication, op. cit., which previously discloses pollution abatement properties of combusting oil shale with MSW. Boardman abstracts the Clayson findings and separately applies the prior art alternatively to coal combustion claiming a method of decreasing pollutants in a thermal conversion process by taking the existence of a concurrent pollution generating process being injected with oil shale for its sorbent and kerogen properties to sequester during combustion any pollutants generated during the thermal conversion process. Specifically, Boardman, et. al., (U.S. Pat. No. 7,384,615) discloses a method of decreasing pollutants produced in a combustion process. The method comprises combusting coal in a combustion chamber to produce at least one pollutant selected from the group consisting of a nitrogen-containing pollutant, sulfuric acid, sulfur trioxide, carbonyl sulifde, carbon disulifde, chlorine, hydroiodic acid, iodine, hydrolfuoric acid, fluorine, hydrobromic acid, bromine, phosphoric acid, phosphorous pentaoxide, elemental mercury, and mercuric chloride. Oil shale particles are introduced into the combustion chamber and are combusted to produce sorbent particulates and a kerogen reductant. The at least one pollutant is contacted with at least one of the sorbent particulates and the kerogen reductant to decrease an amount of the at least one pollutant in the combustion chamber. The kerogen reductant may chemically reduce the at least one pollutant to a benign species. The sorbent particulates may adsorb or absorb the at least one pollutant. A combustion chamber that produces decreased pollutants in a combustion process is also disclosed. Boardman (U.S. Pat. No. 7,708,964) also claims pollution control substances may be formed from the combustion of oil shale, which may produce a kerogen-based pyrolysis gas and shale sorbent, each of which may be used to reduce, absorb, or adsorb pollutants in pollution producing combustion processes, pyrolysis processes, or other reaction processes. Pyrolysis gases produced during the combustion or gasification of oil shale may also be used as a combustion gas or may be processed or otherwise refined to produce synthetic gases and fuels.
Alternatively, Hatfield, et. al. (U.S. Pat. Pub. No. US2008/0202985A1) when used in apparatus and process combination with Coates (U.S. Pat. Pub. No. US2010/0294700A1) carefully controls lower temperatures and processing times to efficiently capture higher quality lighter gravity API oils derived from oil shale using an improved rotary kiln and resulting improved processing methods of the off-take hydrocarbons. Hatfield discloses a continuous, efficient surface method for thermal recovery of hydrocarbons from a solid feedstock which includes a self-contained process that produces hydrogen for upgrading the hydrocarbons to produce motor fuel. The hydrogen also is used as a clean burning fuel for the thermal processing. The hydrogen is produced as a component of synthesis gas formed by gasification of coal. The synthesis gas is processed to remove and dispose of carbon dioxide and by-product sulfur. Combustion of the hydrogen to provide indirect heating of the solid feedstock maximizes hydrocarbons that can be upgraded and reduces or eliminates the emission of carbon dioxide into the atmosphere.
Coates, et. al., (U.S. Pat. Pub. No. US2010/0294700A1) disclosed an apparatus and method, also used in close conjunction with the Hatfield's et. al. efficient surface art (U.S. Pat. Pub. No. US2008/0202985A1), for achieving improved throughput capacity of indirectly heated rotary kilns used to produce pyrolysis products such as shale oils or coal oils that are susceptible to decomposition by high kiln wall temperatures. High throughput is achieved by firing the kiln such that optimum wall temperatures are maintained beginning at the point where the materials enter the heating section of the kiln and extending to the point where the materials leave the heated section. Multiple high velocity burners are arranged such that combustion products directly impact on the area of the kiln wall covered internally by the solid material being heated. Firing rates for the burners are controlled to maintain optimum wall temperatures.